The present invention relates to a lens barrel and a cam barrel molding die, and more particularly, it relates to a lens barrel included in a zoom lens and having movable multi-barrel and multi-lens built-in in combination with a cam barrel of synthetic resin, and a molding die used to produce such a cam barrel.
Japanese Patent Laid-Open No. H09-203850 discloses a mechanical assembly of a zoom adjusting element of a zoom lens which is made of synthetic resin and integrated with a cam element or a cam follower of cam mechanism.
Japanese Patent Laid-Open No. H09-203851 discloses a zoom lens which has a movable frame provided with a cam in relation with a first group of lenses, and a zoom adjusting ring having its inner surface formed with a cam follower in relation with the first group of lenses and also formed with a cam in relation with a second group of lenses, so that simply regulating the zoom adjusting ring enables the first and second groups of lenses to move relative to an optical axis.
Japanese Patent No. 2773586 discloses a zoom lens including a cam ring which has its raised cams molded with opposite cam faces, respectively, by die-cutting in directions along the optical axis, and the invention is characterized in that the cam face shaped by a static member of the die and the cam face shaped by a movable member of the die meet each other at parting line or seam along a raised portion made by the static and movable members of the die.
Japanese Patent Application No. H11-265765 discloses a zoom lens which has a cam barrel made of synthetic resin and formed with a cam in relation with a first group of lenses and cams in relation with at least two more groups of lenses, i.e., second, third, and so forth.
The cam ring having raised cams as described in Japanese Patent No. 2773586, which is suitable for use in a zoom lens, is molded by die-cutting in directions along the optical axis, and this unable to create the raised cams even partially lined up fore and behind one another along the optical axis, which resultantly disturbs down-sizing as having strongly been demanded recently.
The zoom lens set forth in Japanese Patent Application No. H11-265765 is configured to have the cam barrel provided with the cam in relation with the first group of lenses and the two or more cams in relation with the second and other groups of lenses. With this configuration, as can be seen in FIG. 6, the die is adapted to radially slide under a certain restriction in direction so as not to leave undercuts in locations of raised cams for the respective lens groups, and such restriction to and a design of the die lead to a creation of parting line 202 in cam surfaces of cam grooves 200 defined in the molded cam barrel. Consequently, in adjusting for the zooming, studs fitted in the cam grooves 200, while sliding along the cam surfaces of the cam grooves 200, bump into the parting line 202 with slight impact, namely, a light shock of tapping.
The present invention is intended to overcome the above-mentioned disadvantages of the prior art lens barrel of synthetic resin, and it is an object of the present invention to provide a lens barrel having a cam barrel which is molded by die-cutting in radial and other directions relative to the optical axis so as to have raised cams without undercuts if the raised cams are even partially lined up fore and behind one another along the optical axis, and a cam barrel molding die in which a cause of an undercut is eliminated.
It is another object of the present invention to provide a lens barrel having a cam barrel where there is no parting line in either the cam grooves nor the raised cams, and a cam barrel molding die to produce such a cam barrel.
A lens barrel according to the present invention includes a cam barrel which has its outer surface provided with raised cams and is made of synthetic resin, and in the cam barrel, each of the raised cams has at least one of cam faces inclined toward an opposite cam face off a radial direction relative to an optical axis of the cam barrel.
In another aspect of the present invention, a cam barrel, which is included in a lens barrel and made of synthetic resin, has cam grooves and raised cams in its outer surface, and each of the raised cams has at least one of cam faces inclined toward an opposite cam face off a radial direction relative to an optical axis of the cam barrel.
Furthermore, a die according to the present invention is designed to mold a cam barrel of synthetic resin which is suitable for use in a lens barrel and has raised cams in its outer surface, and each of the raised cams has at least one of cam faces inclined toward an opposite cam face off a radial direction relative to an optical axis of the cam barrel, so as not to leave an undercut in the raised cams.
In another aspect of the present invention, a die is designed to mold a cam barrel of synthetic resin which is suitable for use in a lens barrel and has cam grooves and raised cams in its outer surface, and each of the raised cam s has at least one of cam faces inclined toward an opposite cam face off a radial direction relative to an optical axis of the cam barrel, so as not to leave an undercut in either the cam grooves or the raised cams.
These embodiments of the present invention are commonly characterized in that one of the cam faces extends in a radial direction relative to the optical axis. If both the cam faces of each of the raised cams are inclined toward the opposite cam faces off the radial direction relative to the optical axis, both the cam faces and cam followers must be shaped with high precisions. Additionally, short shot in molding is likely to occur where fused resin is insufficient at the top of the raised cam that is to be tapered in shape, which results in the truncated top of the raised cam being unsatisfactory in hardness.